Page:Popular Science Monthly Volume 56.djvu/464

450 to considerable distances from a vessel in a raging sea, so that the oil, as it diffuses, may still the waters in her course; while sounding-lines may be thrown far in advance of a vessel while she is still under way, and the soundings taken without her laying-to.

Inclosed in shallow tin boxes, which are fixed by lead strips to the top of the rail, explosives are used as torpedoes in the railroad service to give warning, by the report of their explosion as an engine runs over them, that another train is on the same track and but a short distance ahead, and by this means collisions in fogs or on curves are frequently prevented.

Explosives find applications in many industries. The farmer uses them in breaking bowlders, grubbing stumps and felling trees, in shaking the soil to fit it for deep-soil cultivation, and, in the wine-growing districts, to free it from phylloxera, while the farmer's friend has tried by this means, in times of drought, to shake the nerves of Jove and to divert the hailstorm from its course.

The iron founder uses them in breaking up large castings. The iron smelter employs them to clear out obstructions in blast furnaces while the latter are still in operation, the dynamite, protected by a clay envelope, being inserted in the red hot mass which clogs the furnace. The author has proposed to use the detonating explosives for testing the integrity of large masses of metals and their resistance to shock.

Dynamite has been employed in fishing, since submarine explosions of it will kill or stun fish for a long distance about the charge. This method of fishing, which threatened to deplete the waters, has very properly been prohibited by law, but guns are employed for projecting harpoons in the whale fishery, and have reduced very much the danger attending this extra-hazardous occupation.

Nitroglycerin, inclosed in tin cans three to five inches in diameter and five to twenty-five feet in length, is used for shooting oil wells to free them from the solid paraffins with which they become choked, or to shake the oil-bearing sandstone so as to produce a greater yield. In this work the loaded can, having a detonating cap attached to its top, is lowered by a wire to the bottom of the well.